1. Field of the application
The present invention relates to rolling production, and more particularly, to roll mill stands.
The roll mill stands according to the present invention can most advantageously be employed in rolling mills for producing billets, sections and pipes from poorly plastic, hard-to-deform metals, such as, nickel, tungsten, molybdenum, their alloys and high-alloy grades of steel. These metals and alloys currently find an ever expanding field of application.
In plastic working, these materials feature a poor plasticity and a high resistance to deformation which exceeds by many times that of carbon steels.
Therefore, the rolling of these materials calls for the roll mill stands which create a favourable pattern of uniform compression deformations and possess a high loading capacity. In addition, said materials cover a wide range of grades and are used to manufacture many types and sizes of products, this necessitating frequent pass re-adjustments and roll changes in the process of operations, so that the roll mill stands are required to possess broad process potentialities.
2. Description of the Prior Art
There is known a roll mill stand with a four-roll pass. The known roll mill stand has four work rolls with axes thereof being set at 90.degree. one with respect to another. These rolls are mounted in shells secured rigidly between two housings, all the rolls being live.
This roll mill stand is intended mainly to roll billets of a single size from ingots obtained in continuous casting machines and having a low plasticity. The pass, formed with four rolls, provides a favourable pattern of stressed state (uniform compression) which enhances the plasticity of the metal being rolled. In this roll mill stand, termed hereinafter simply stand, a wear of the working surface of rolls necessitates a complete disassambly of the stand, inclusive of the dismantling of shells with work rolls, for replacing the latter. This operation requires much time and labour and thus considerably lowers the efficiency of the stand.
In addition, there are known roll mill stands comprising a supporting frame which carries two housings, with two shell-mounted work rolls being arranged therebetween. Each shell is hinged upon one of the housings by means of a pivot parallel to the centre line of the work roll, and is secured in the other housing with the aid of a screw-down mechanism.
In these stands, the hinged connection of the shell to the housing permits the change of work rolls to be made by rotating the housing about a pivot set in the housing, whereas the fixing of the shell to the other housing by means of a screw-down mechanism makes it possible to adjust the radial gap between the rolls.
However, these stands are intended to roll thin sheets only.